Since a steering apparatus of a vehicle is to be used (for steering) by many and unspecific drivers, it is desirable that the position of a steering wheel is adjustable in compliance with the physique or the posture of each driver. In order to satisfy such desire, a tilt adjusting mechanism or a telescopic adjusting mechanism is widely employed not only for passenger cars, but also for freight cars.
The tilt adjusting mechanism is a mechanism to adjust the position of a steering wheel in the up-and-down direction, and is constituted by a tilt pivot for rockably supporting a steering column and a tilt position fixing means for fixing the steering column at a desired position (rocking angle). On the other hand, the telescopic adjusting mechanism is a mechanism for adjusting the position of the steering wheel in the back-and-forth direction (the axial direction of the steering shaft), and is constituted by an expandable unit of a double tube type or the like to be used for expansion and/or contraction of the steering shaft and a telescopic position fixing means for fixing the steering shaft at a desired position (with an amount of expansion/contraction).
Hitherto, it is general that, as the tilt position fixing means, a distance bracket formed of a steel plate is connected to a steering column formed of a steel pipe by welding and this distance bracket is pressed to be fixed by a body-side bracket which is formed of a steel plate. However, with such an arrangement, the number of the constituent parts and that of the welding steps are increased, and moreover, variable inconveniences are inevitably caused by thermal distortion, etc., at the welding. As a result, it is proposed in Japanese Patent Application Laid-Open No. 10-7003 or the like (hereinafter called the prior art) a structure in which a distance unit for fixing the steering column on the body-side bracket is formed to be expanded by plastic working.
FIG. 7 is a perspective view showing a steering column of the prior art as a single unit, and FIG. 8 is a vertical cross-sectional view of a distance unit of a steering column supported by a body-side upper bracket in a steering column apparatus. This steering column 21 is formed of a steel pipe in a cylindrical form, and pressed portions 25, 27 are formed to be expanded in the lower portions of the distance unit 29 in FIG. 7 and FIG. 8. Pressed surfaces 51, 53 are formed on side surfaces of the pressed portions 25, 27, and a through hole 71, through which a tilt bolt 31 is inserted, is formed on each of the pressed surfaces 51, 53. In this steering column apparatus, a nut 33 advances to the tilt bolt 31 by thread-engagement therewith upon rotation of a tilt adjusting lever 35 which is disposed on a side surface of the body-side bracket 3, so as to compress and release the steering column 21 by the use of the body-side bracket 3. According to the steering column apparatus of the prior art, it is possible to reduce the number of the constituent parts and that of the welding steps to reduce the manufacturing cost, and at the same time, to prevent inconveniences which may be caused by the thermal distortion or the like at the welding.
However, the above-described steering column apparatus of the prior art has the following drawbacks. For example, when a driver fastens the tilt lever 35, the parts other than the pressed portions 25, 27 in the distance unit 29 (the upper and lower portions in FIG. 9) are flexed, so that the operative feeling becomes very bad and a secured fixing of the steering column 21 by the use of the body-side bracket 3 becomes unfeasible. Moreover, when the driver clamps the tilt lever 35 with a clamping force exceeding a predetermined value, the distance unit 29 may be flexed beyond the limit of its elasticity so as to be plastically deformed. Then, these inconveniences become conspicuous when the steering column is formed of a thin steel pipe, which results in an obstacle to reduction of the weight of the steering apparatus.